The link that LucD provided shows the way to do it. Here's a function that I have added to scripts to do it. You can just loop through a list of VM names and pass them into the function.
Write-Host "Configuring VMTools upgrade setting"
$vmview = Get-vm $vm | Get-View
$vmConfigSpec = New-Object VMware.Vim.VirtualMachineConfigSpec
$vmConfigSpec.tools = New-Object VMware.Vim.ToolsConfigInfo
$vmConfigSpec.Tools.ToolsUpgradePolicy = "UpgradeAtPowerCycle"
$vmConfigSpec.Tools.syncTimeWithHost = $true
$vmview.ReconfigVM_task($vmConfigSpec) | Out-Null